well, mirena causes many of us not to ovulate. Without ovulation, our ovaries do not make progesterone. there's also other data supporting a reduction in natural progesterone from the mirena. Just wanted to add that, since it sounds like you have a nasty idiot for a doc who is totally wrong about your body producing the same amount of progesterone! I am sorry you had to deal with that- anyone who can be that insensitive, whether they agree or disagree with us, should find another profession.